The subject matter disclosed herein relates generally to imaging systems, and more particularly to an apparatus and method for motion-correcting medical images.
Multi-modality imaging systems scan using different modalities, for example, computed tomography (CT) and positron emission tomography (PET) imaging. During operation, the image quality may be affected by the motion of the object being imaged. More specifically, image artifacts are produced by movement of the object during image acquisition. Respiratory motion is a common source of involuntary motion in mammals (e.g., people and animals) encountered in medical imaging systems. The respiratory motion may lead to errors during image review, such as when a physician is determining the size of a lesion, determining the location of the lesion, or quantifying the lesion.
Moreover, in multi-modality systems, for example, an integrated PET/CT system, the PET and CT images should be registered with one another. However, since the CT images are typically acquired during a short time period, the attenuation map generated by the CT images represents the attenuation characteristics of the patient during a portion of the breathing cycle where there is minimal breathing motion. In contrast, the PET images are typically acquired over a relatively long time period where a patient is allowed to breathe freely due to the long acquisition time. The mismatch in attenuation properties due to respiration between the two data acquisition modes may result in image artifacts in the attenuation corrected PET images.
One known method for reducing the imaging artifacts is to use a plurality of respiratory gated CT images to generate attenuation correction maps that better match the respiratory characteristics of a respiratory gated PET acquisition. A further method may include requesting the patient to hold their breath during the scan. However, because PET data may be acquired over several minutes, the patient typically has to breathe several times during the PET acquisition, potentially resulting in image artifacts.